P0380 — Glow plug/heater circuit A malfunction

P0380: Glow plug/heater circuit A malfunction — what it means, the affected system and what to check before replacing parts.

Meaning, symptoms, causes and checks

The definition identifies a malfunction in glow-plug/heater circuit A. It identifies the monitored circuit but does not by itself distinguish one glow plug, a shared power supply, relay or control module, connector, harness or current-monitoring fault; circuit grouping and test limits depend on the diesel engine and vehicle.

Affected system: Glow-plug/heater control

Symptoms

  • Hard cold starting and unstable idle after startup.

Possible causes

  • Faulty glow plugs, relay/fuse fault or damaged wiring.

What to check

  • Test glow plugs individually and check relay, fuse and connections.

Also written as: P0380-00, P038000, PO380 (some scan tools add the fault-type byte, e.g. -00).